Revert "Stop CMake warning about @rpath on Mac OS X."

This reverts commit c9f00dfb9f5ce306398f18cafa143988a4f61515. Because it breaks
under CMake versions that don't know what CMP0042 is.
amqp-consume: support consuming N messages at a time

If you have a single consumer C₁ and 10 messages are published, all 10
will be streamed to that one customer. Assume each message takes a few
minutes to be handled.

If a second consumer C₂ comes up before C₁ is able to process its first
message, it will stay idle until new messages are published, while C₁
will still have to process the other 9 messages after finishing with the
first one.

If both consumers were started with `--messages 1`, C₁ would only fetch
a single message, and start handling it; C₂ would start and already
receive the second message .
Preparation for v0.5.2 release.
Bumping revision for development.
Fix spelling in comment for amqp_socket_writev()
Enable SSL support for tools too.

In tools/common.c `#ifdef WITH_SSL` is used but never defined if SSL support is
desired.
Regen amqp_framing.[ch] to include autogend docs.

Doing this because the next change will cause a ton of diffs otherwise.
Enable auto_delete & internal for exchange.declare

Enable auto_delete and internal parameters of amqp_exchange_declare() in
codegen. These were once not generated because RabbitMQ did not support these
parameters. The broker now supports these and so should we.

This fixes #218
Use amqp_cstring_bytes() to specify locale field.
Add properties table merge function.
Add auth failure client capability as default.
Handle connection.close on auth failure.
Add CMocka as test dependency.